1. Field of the Invention
The present invention relates to start-up reset circuits and related methods, and more particularly, to start-up reset circuits and related methods adaptive to low voltage systems.
2. Description of the Prior Art
In current electronic devices, in order to make the circuit therein operate normally, it is typical to send a start-up reset signal (which is typically labeled as “RESET”) to all circuit components that require reset operations to have correct initial values, to ensure correct further operations.
A conventional start-up reset circuit utilizes a comparator to compare a reference voltage with a voltage source Vdd within an integrated circuit (IC), wherein the reference voltage can be generated by a bandgap voltage generator. Architecture and functions of the bandgap voltage generator are well known in the art, and therefore not explained in detail here. FIG. 1 illustrates a conventional start-up reset circuit 100. As shown in FIG. 1, the conventional start-up reset circuit 100 comprises a comparator 102 and a bandgap voltage generator 104. Once the circuit starts up, the comparator 102 compares the voltage source Vdd and a reference voltage Vref from the bandgap voltage generator 104 to output a start-up reset signal RESET. During this, in an initial phase of the circuit start-up, the voltage source Vdd continuously increases while the reference voltage Vref is kept constant. If the voltage source Vdd is lower than the reference voltage Vref, the start-up reset signal RESET is set as logic 1 (i.e. a high voltage level here) to perform operations of start-up reset; otherwise, the start-up reset signal RESET is set as logic 0 (i.e. a low voltage level here) to stop performing operations of start-up reset.
According to the prior art, as the chip area required for the circuit thereof (for example, the comparator or the bandgap voltage generator) is large, the power consumption is correspondingly high. In addition, as semiconductor technologies progress rapidly, the internal circuit scale of ICs becomes smaller and smaller, and internal circuits and circuit configurations of various components are more complicated. Accordingly, semiconductor processes are forced to approach a tiny scale such as the order of nanometers. As a result, the voltage source Vdd required for the internal circuits becomes smaller and smaller accordingly. Regarding this, the start-up reset circuit of the prior art is not able to operate normally under a lower value of the voltage source Vdd.
As mentioned, the start-up reset circuit of the prior art is complicated and the chip area required is large. Furthermore, the power consumption is correspondingly high. Therefore, it is necessary to solve the above problems and other problems that will be faced when semiconductor processes are forced to approach the tiny scale mentioned above.